My impression is rather different. The automatic conversion tools and compatibility libraries were only provided several years and versions into the v3 transiti

My impression is rather different. The automatic conversion tools and compatibility libraries were only provided several years and versions into the v3 transition because the community was demanding it so hard and most users refused to do anything with v3 without it. Most of it probably wouldn't have been necessary at all, or would have been there on day 1, if they had made backwards compatibility the priority instead of going hard on the everyone rewrite everything to the new v3 style right away. I'm sure they didn't want to support Python 2 for 12 years but were instead basically forced to because the transition was so difficult for so many major projects.